Resin-sealed semiconductor device and method of manufacturing the device

ABSTRACT

A resin-sealed semiconductor device according to this invention is an LOC type semiconductor device comprising a semiconductor chip having a circuit surface on which an electrode is formed; a lead which is arranged in such a manner that the distal end of the lead overlaps the semiconductor chip, and which is electrically connected to each electrode; a lead fixing resin layer interposed between the semiconductor chip and the lead to fix them; and a sealing resin layer coated to cover the semiconductor chip and the lead. The diameter of filler contained in the lead fixing resin layer is about {fraction (1/10)} to ⅕ the diameter of filler contained in the sealing resin layer, and is about {fraction (1/10)} a gap between the lead and the semiconductor chip.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a resin-sealed semiconductordevice such as an IC or an LSI and a method of manufacturing the same.

[0002] A resin-sealed semiconductor device comprises a semiconductorchip and a lead connected to the electrode of the semiconductor chip.The distal end of the lead and the semiconductor chip are sealed by aresin. The whole size of the resin-sealed semiconductor device includingthe sealing resin is determined by the standards. And generally, thesize of the semiconductor chip increases as the degree of integration ofthe circuit increases. When the semiconductor chip increases in size andwhen the distal end of the lead is arranged not to overlap thesemiconductor chip, length of a part of the lead fixed with the resin isshortened, and the lead cannot be rigidly fixed. Therefore, in thiscase, an LOC (Lead On Chip) type structure in which the distal end ofthe lead overlaps a semiconductor chip is generally employed.

[0003] Japanese Patent Application Laid-Open No. 61-218139 discloses anLOC type resin-sealed semiconductor device. In the structure disclosedin this publication, as shown in FIG. 5, the distal end of a lead 1 isadhered to a semiconductor chip 3 through an insulating tape 4, and thedistal end and an electrode lb of the semiconductor chip 3 are connectedto each other with a bonding wire 5. The semiconductor chip 3, thedistal end of the lead 1, and the bonded portions are covered with thesealing resin layer 2.

[0004] The sealing resin layer 2 generally consists of an epoxy-basedresin whose ratio by weight is about 20% and filler whose ratio byweight is about 80%. The filler is silica-based solid bodies each havinga diameter of 50 to 100 μm and has a function of keeping the hardness ofa resin layer and a function of suppressing thermal expansion.

[0005] However, since the above insulating tape 4 easily absorbsmoisture, the moisture contained in the insulating tape 4 is steamed byheat generated in practical use. Force generated in this casedisadvantageously makes cracks 6 in the sealing resin layer 2 as shownin FIG. 6.

[0006] As shown in FIG. 7, if the large-diameter filler 7 is clogged ina gap of about 100 Am between the lead 1 and the semiconductor chip 3,stress is generated between the lead 1 and the semiconductor chip 3 whenthe sealing resin layer 2 is solidified. The stress is generated due tothe difference between the coefficient of contraction of the sealingresin layer 2 and that of the filler 7. This stress may make flaws 8such as cracks in the semiconductor chip 3.

SUMMARY OF THE INVENTION

[0007] The present invention aims to solve the problems of the prior artdescribed above, and its object is to provide a resin-sealedsemiconductor device which employs an LOC type structure, suppressesformation of cracks in a sealing resin layer by heat in practical use,and can prevent flaws or cracks from being formed in a semiconductorchip in solidification of the sealing resin layer.

[0008] A resin-sealed semiconductor device according to the presentinvention comprises: a semiconductor chip having a circuit surface onwhich a plurality of electrodes are formed; a plurality of leads whichare arranged at predetermined gaps with respect to the semiconductorchip in such a manner that distal ends of the leads overlap thesemiconductor chip, and which electrically connected to the respectiveelectrodes; a lead fixing resin layer filled between the semiconductorchip and the leads to fix the leads to the semiconductor chip; and asealing resin layer which is coated to cover the distal ends of theleads and the semiconductor chip, and when the lead fixing resin layercontains filler, the diameter of the filler is smaller than the diameterof filler contained in the sealing resin layer, or the lead fixing resinlayer is free from filler.

[0009] When the lead fixing resin layer contains filler, the diameter ofthe filler is preferably about {fraction (1/10)} to ⅕ the diameter ofthe filler contained in the sealing resin layer, or the diameter ispreferably about {fraction (1/10)} an gap between the leads and thesemiconductor chip at an overlapping portion therebetween, i.e., thediameter is preferably about 10 μm. In addition, a ratio by weight ofthe filler contained in the lead fixing resin layer is preferably lowerthan a ratio by weight of the filler contained in the sealing resinlayer.

[0010] A method of manufacturing a resin-sealed semiconductor deviceaccording to the present invention which is constituted by sealing asemiconductor chip and leads with a sealing resin layer, comprises: thestep of coating a lead fixing resin layer on a circuit surface of thesemiconductor chip; the step of fixing the distal ends of a plurality ofleads to the semiconductor chip with the lead fixing resin layer; thestep of bonding the distal ends of the leads and electrodes formed onthe circuit surface; and the step of sealing the semiconductor chip andthe leads with the sealing resin layer. The lead fixing resin layercontains filler having a diameter smaller than that of filler containedin the sealing resin layer, or is free from filler.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a partially sectional view of a resin-sealedsemiconductor device according to an embodiment of the presentinvention;

[0012]FIG. 2(A) is a side view of a semiconductor chip in the deviceshown in FIG. 1, and FIG. 2(B) is a plan view of the semiconductor chipin FIG. 2(A);

[0013]FIG. 3(A) is a side view showing a state wherein a resin for alead fixing resin layer is coated on the semiconductor chip in FIG. 2,and FIG. 3(B) is a plan view showing the state in FIG. 3(A);

[0014]FIG. 4(A) is a side view showing a state wherein a lead is fixedto the semiconductor chip shown in FIG. 3, and FIG. 4(B) is a plan viewshowing the state in FIG. 4(A);

[0015]FIG. 5 is a partially sectional view of a conventionalresin-sealed semiconductor device;

[0016]FIG. 6 is a partially sectional view showing a problem of theconventional resin-sealed semiconductor device; and

[0017]FIG. 7 is a partially sectional view showing another problem ofthe resin-sealed semiconductor device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] An embodiment of a resin-sealed semiconductor device according tothe present invention will be described below.

[0019] A resin-sealed semiconductor device according to this embodiment,as shown in FIG. 1, is an LOC type semiconductor device comprising asemiconductor chip 3, a lead 1, a lead fixing resin layer 9 and asealing resin layer 2.

[0020] The semiconductor chip 3 is provided with a circuit surface 3 a(serving as an upper surface in FIG. 1), and an electrode 10 is formedon the circuit surface 3 a. The lead 1 is arranged at a predeterminedgap with respect to the semiconductor chip 3 in such a manner that thedistal end of the lead 1 overlaps the semiconductor chip 3.

[0021] A bonding wire 5 electrically connects the distal end of the lead1 and the electrode 10. The lead fixing resin layer 9 is filled betweenthe semiconductor chip 3 and the lead 1 to fix the lead 1 to thesemiconductor chip 3. The sealing resin layer 2 coated to cover thesemiconductor chip 3 and the lead 1.

[0022] The electrode 10 is formed on the semiconductor chip 3 such thata plurality of electrodes 10 are arranged in two lines at the centralportion of the circuit surface 3 a as shown in FIG. 2(A) serving as theside view and FIG. 2(B) serving as the plane view. The lead 1 connectedto the electrodes 10 is formed such that a plurality of leads 1 arearranged in correspondence with the number of electrodes.

[0023] The gap between the circuit surface 3 a of the semiconductor chip3 and the distal end of the lead 1 is about 40 to 100 μm. The leadfixing resin layer 9 is filled between the lead 1 and the circuitsurface 3 a over a range from the distal end of the lead 1 to theperiphery of the semiconductor chip 3, i.e., a range in which the lead 1overlaps the semiconductor chip 3.

[0024] The sealing resin layer 2 contains filler having a diameter of 50to 100 μm at a ratio by weight of about 80%, and the remaining 20% is anepoxy-based resin. On the other hand, the lead fixing resin layer 9 alsoconsists of filler and an epoxy-based resin. However, the diameter ofthe filler is about {fraction (1/10)} to ⅕ the diameter of the fillercontained in the sealing resin layer 2, and is about {fraction (1/10)}the gap between the lead 1 and the semiconductor chip 3 at theoverlapping portion therebetween. The ratio by weight of the fillercontained in the lead fixing resin layer 9 is set to be lower than theratio by weight of the filler contained in the sealing resin layer 2.More specifically, the lead fixing resin layer 9 contains filler whichhas a diameter of about 10 μm and whose ratio by weight is about 40%,and the remaining 60% consists of an epoxy-based resin.

[0025] As described above, when the resin layer 9 is used in place of aconventional insulating tape to fix the lead 1, a moisture content inthe fixed portion decreases. For this reason, steam generated by heat inpractical use can be suppressed, and probability of forming cracks inthe sealing resin layer 2 can be reduced. When the filler content issmaller than that in the sealing resin layer 2, probability of cloggingfiller between the lead 1 and the circuit surface 3 a can be reduced.When the diameter of filler itself is reduced, the filler can beprevented from being clogged. Therefore, stress based on the differencebetween the coefficient of contraction of the resin and the coefficientof contraction of the filler in solidification of a sealing resin can beprevented from being generated, so that the semiconductor chip 3 can beprevented from being cracked.

[0026] Although the above example explains a case wherein the leadfixing resin layer 9 contains filler, a material being free from fillercan also be used as the lead fixing resin layer 9.

[0027] A method of manufacturing a resin-sealed semiconductor deviceaccording to the embodiment will be described below. This manufacturingmethod comprises: the first step of coating the lead fixing resin layer9 on the circuit surface 3 a of the semiconductor chip 3; the secondstep of fixing the distal ends of the plurality of leads 1 to thesemiconductor chip 3 with the lead fixing resin layer 9; the third stepof bonding the distal ends of the leads 1 and the electrodes 10 formedon the circuit surface 3 a to each other; and the fourth step of sealingthe semiconductor chip 3 and the leads 1 with the sealing resin layer 2.The respective steps will be sequentially described below.

[0028] In the first step, as shown in FIG. 3(A) serving as a side viewand FIG. 3(B) serving as a plan view, a resin 9 a for forming the leadfixing resin layer 9 is liquefied, and the liquid resin 9 a is suppliedfrom a dispenser 11 onto the circuit surface 3 a. The resin 9 a iscoated on a position where the leads 1 are fixed, i.e., both the sidesof electrode rows in the arrangement direction of the electrodes 10. Thecoated liquid resin 9 a initially formes hemisphere shape in the firststep.

[0029] In the second step, as shown in FIG. 4(A) serving as a side view,the semiconductor chip 3 is set in a recessed portion 12a formed in aheat block 12, and the plurality of leads 1 are pressed against theliquid resin 9 a from the upper side of FIG. 4(A) to spread the liquidresin 9 a. The heat block 12 is kept at a temperature of 80° C. to 100°C., and the lead fixing resin layer 9 serving as a thermosetting resinis solidified for about one minute. The depth of the recessed portion 12a is set such that the level of the circuit surface 3 a is lower than aperiphery surrounding surface of the recessed portion 12 a by 40 to 100μm. The lead 1 is arranged to extend from both the sides of thesemiconductor chip 3 to the central electrode 10 as shown in FIG. 4(B)serving as a plan view, and the lead 1 is fixed to the semiconductorchip 3 with the lead fixing resin layer 9.

[0030] In the third step, the electrode 10 of the semiconductor chip 3is electrically connected to the distal end of the lead 1 fixed to thesemiconductor chip 3 in the second step by bonding with the wire 5. Andin the fourth step, the semiconductor chip 3, the distal end of the lead1, and the wire 5 are sealed with the sealing resin layer 2, and thesealing resin layer 2 is solidified. Thereafter, lead processes such asdiver cutting, lead cutting, and lead bending are performed to completethe semiconductor device shown in FIG. 1.

[0031] As described above, according to the present invention, when alead fixing resin layer is used to fix a lead before bonding to asemiconductor chip, a moisture content in the fixed portion decreases.For this reason, steam generated by heat in practical use can besuppressed, and probability of forming cracks in the sealing resin layercan be reduced. In addition, when the diameter of filler contained inthe lead fixing resin layer is reduced, probability of clogging thefiller between the lead and the semiconductor chip can be reduced. Whenthe diameter of filler itself is reduced, the filler can be preventedfrom being clogged, and the semiconductor can be prevented from beingcracked in solidification of the sealing resin.

[0032] Furthermore, when the filler content in the lead fixing resinlayer is made smaller than that in the sealing resin layer, probabilityof clogging filler between the lead and the circuit surface can bereduced. When a resin being free from filler is used, filler cloggingcan be canceled. In this manner, stress based on the difference betweenthe coefficient of contraction of the resin and the coefficient ofcontraction of the filler in solidification of the sealing resin can beprevented from being generated, so that the semiconductor chip can beprevented from being cracked.

What is claimed is:
 1. A resin-sealed semiconductor device comprising: asemiconductor chip having a circuit surface on which a plurality ofelectrodes are formed; a plurality of leads which are arranged atpredetermined gaps with respect to said semiconductor chip in such amanner that distal ends of said leads overlap said semiconductor chip,and which electrically connected to said respective electrodes; a leadfixing resin layer filled between said semiconductor chip and said leadsto fix said leads to said semiconductor chip; and a sealing resin layerwhich is coated to cover the distal ends of said leads and saidsemiconductor chip which are fixed with said lead fixing resin, whereinboth said lead fixing resin layer and said sealing resin layer containfiller, the diameter of the filler contained in said lead fixing resinlayer is smaller than the diameter of filler contained in said sealingresin layer.
 2. A resin-sealed semiconductor device according to claim1, wherein the diameter of the filler contained in said lead fixingresin layer is about {fraction (1/10)} to ⅕ the diameter of the fillercontained in said sealing resin layer.
 3. A resin-sealed semiconductordevice according to claim 1, wherein the diameter of the fillercontained in said lead fixing resin layer is about {fraction (1/10)} agap between said leads and said semiconductor chip at an overlappingportion therebetween.
 4. A resin-sealed semiconductor device accordingto claim 1, wherein the diameter of the filler contained in said leadfixing resin layer is about 10 μm.
 5. A resin-sealed semiconductordevice according to claim 1, wherein a ratio by weight of the fillercontained in said lead fixing resin layer is lower than a ratio byweight of the filler contained in said sealing resin layer.
 6. Aresin-sealed semiconductor device comprising: a semiconductor chiphaving a circuit surface on which a plurality of electrodes are formed;a plurality of leads which are arranged at predetermined gaps withrespect to said semiconductor chip in such a manner that distal ends ofsaid leads overlap said semiconductor chip, and which electricallyconnected to said respective electrodes; a lead fixing resin layerfilled between said semiconductor chip and said leads to fix said leadsto said semiconductor chip; and a sealing resin layer which is coated tocover the distal ends of said leads and said semiconductor chip whichare fixed with a lead fixing resin, wherein said lead fixing resin layeris free from filler.
 7. A method of manufacturing a resin-sealedsemiconductor device which is formed by sealing a semiconductor chip andleads with a sealing resin layer, comprises: the step of coating a leadfixing resin layer, which contains filler having a diameter smaller thanthat of filler contained in said sealing resin layer, on a circuitsurface of said semiconductor chip; the step of fixing the distal endsof a plurality of leads to said semiconductor chip with said lead fixingresin layer; the step of bonding the distal ends of said leads andelectrodes formed on said circuit surface; and the step of sealing saidsemiconductor chip and said leads with said sealing resin layer.
 8. Amethod of manufacturing a resin-sealed semiconductor device which isformed by sealing a semiconductor chip and leads with a sealing resinlayer, comprises: the step of coating a lead fixing resin layer, whichis free from filler, on a circuit surface of said semiconductor chip;the step of fixing the distal ends of a plurality of leads to saidsemiconductor chip with said lead fixing resin layer; the step ofbonding the distal ends of said leads and electrodes formed on saidcircuit surface; and the step of sealing said semiconductor chip andsaid leads with said sealing resin layer.